SSL devices generally use semiconductor light emitting diodes (“LEDs”), organic light emitting diodes (“OLEDs”), laser diodes (“LDs”), and/or polymer light emitting diodes (“PLEDs”) as sources of illumination rather than electrical filaments, a plasma, or a gas. FIG. 1 is a cross-sectional diagram of a portion of a conventional indium-gallium nitride (“InGaN”) LED 10. As shown in FIG. 1, the LED 10 includes a substrate 12 (e.g., silicon carbide, sapphire, or silicon), an N-type gallium nitride (“GaN”) material 14, an active region 16 (e.g., GaN/InGaN multi quantum wells (“MQWs”)), and a P-type GaN material 18 on top of one another in series.
The GaN/InGaN materials of the LED 10 are generally formed via epitaxial growth and typically include a large number of crystal dislocations. For example, FIG. 2 is a transmission electron microscopy (“TEM”) image 20 of a GaN material 24 formed on a sapphire substrate 22 via metal organic chemical vapor deposition (“MOCVD”). As shown in FIG. 2, the GaN material 24 includes a plurality of threading dislocations 26 extending away from the substrate 22 mainly due to lattice mismatch between the GaN material 24 and the substrate 22.
The large number of threading dislocations 26 may negatively impact the optical and/or electrical performance of the LEDs. For example, it is believed that the threading dislocations 26 can short circuit a P/N junction (e.g., in the active region 16 of the LED 10) and/or cause current leakage in the LEDs. It is also believed that impurities (e.g., carbon (C), oxygen (O), silicon (Si), and hydrogen (H)) tend to aggregate in the cores of the threading dislocations 26. Such impurities can cause non-radiated hole-electron recombination during operation, thus causing low optical efficiencies in the LEDs. Accordingly, several improvements to reduce the number of threading dislocations in LEDs may be desirable.